The present invention relates to an apparatus for producing semiconductors such as an apparatus for moving a table or stage which is used for moving the specimen in a step and repeat camera, reduction projection aligner system or the like.
Generally, in such an apparatus, an integrated circuit pattern is projected and printed opto-photographically on a mask plate or a wafer coated with a photo resist. It is, however, impossible to effect the printing over the entire surface of the mask plate or the wafer at once due to a restriction concerning the image area of the projection lens.
This type of apparatus, therefore, incorporates an apparatus for moving a table or stage (precise X-Y table) to which adhered is the mask plate or the wafer, and printing of the integrated circuit pattern is effected over the entire area of the mask plate or the wafer through a two-dimensional stepping motion in X and Y directions.
In the production of the integrated circuit, it is required to superpose a multiplicity of different circuit patterns, usually 8 to 12 patterns, in layers on a single wafer at a registration accuracy of about 0.2 .mu.m. This means that an equivalent or higher precision is required for the position control of the X-Y table. In addition, there is a demand for a high-speed positioning of the X-Y table to meet the requirement for the improvement in productivity.
To this end, in the X-Y table of the kind described, ball and roller bearing guide using rolling members such as balls and rollers or an air bearing guide has been used as the guide for the rectilinear motion of the X-Y table.
The ball and roller bearing guide, however, has to be fabricated with a severe selection and uniformity of the rolling members and must be worked with high precision, in order to achieve the required high accuracy of movement of the X-Y table. Thus, the production is not easy and it is quite difficult to maintain the initial accuracy of movement over a long period of use. The use of the air bearing guide is accompanied with a problem that a considerably long vibration settling time is required partly because of the increased mass of the movable part as a result of increased size of the mechanism as a whole, and partly because of an extremely small friction loss, although it affords a comparatively high accuracy of guiding operation and a good endurance. Thus, the air bearing guide is not suited for the high-speed positioning. Furthermore, there is another problem in these conventional arrangements that the material is limited due to the stress concentration and distortion force applied to the constituents, to hinder the reduction of weight of the movable parts which is one of the requisites for the high-speed positioning operation.